It is often desirable in a variety of applications to provide surfaces to structures with the capability of absorbing radar and similar electromagnetic waves. In so absorbing these waves, a substantially lower magnitude of energy is reflected back to the source of the incident waves.
A variety of prior art absorbers are constructed as separate units that are subsequently positioned over a structure. Such absorbers are known as parasitic absorbers. These absorbers may comprise several layers of resistive material (so called Jauman Absorbers). A typical type of resistive absorber comprises a parasitic carbonyl iron filled rubber panel that is fitted over a given structure. Absorbers can also take the form of a plurality of layers of conductive dipoles sandwiched between dielectric layers. Such dipole absorbers are further described in co-pending U.S. patent application Ser. Nos. 07/177,518 and 07/489,924 now U.S. Pat. Nos. 5,223,849 and 5,214,432, respectively.
Several disadvantages to parasitic versions of the above-described absorbers exist. Parasitic absorbers, in general, add thickness to a structure without increasing its strength. These absorbers also are more prone to damage since they are not integrally formed with the structure. In addition, these absorbers may be more prone to damage by environmental conditions and, more prone to dislodgment from the underlying structure.
In producing layered absorbing structures it has also been necessary to utilize a material having a sufficiently low dielectric constant to obtain sufficiently wide absorption bandwidths. Often, however, such materials do not exhibit sufficient structural strength.
In view of the above-described disadvantages of the prior art, this invention has as one object to provide a material for constructing a layered electromagnetic energy absorbing structure with sufficient strength to serve as an integral part of an overall structure.
It is a further object of this invention to provide an electromagnetic energy absorbing structure that may be constructed with relative ease in a variety of shapes and configurations.
It is yet another object of this invention to provide an electromagnetic energy absorbing structure that substantially reduces or eliminates undesirable backscatter effects that may be present in certain absorbing structures.